1. Field of Invention
The present invention relates to a power monitoring apparatus, and more particularly to a power monitoring apparatus applied to a fan.
2. Related Art
Generally, at least one fan is used to an electronic system for thermal dissipation so as to maintain the electronic system in a normal operating condition. The power of the fan is provided by the electronic system directly or by an external voltage source indirectly. However, if the input voltage generated by the electronic system or the voltage source is abnormal, for example the input voltage is too high or too low, the internal elements of the fan may be damaged. For example, an over current phenomenon is formed when the input voltage is too low and the current rises, and the internal elements of the fan may be damaged. On the contrary, when the input voltage is too high and over the acceptable voltage of the fan, the internal elements of the fan may also be damaged. Typically, an analog control chip is used to perform the voltage detection.
As shown in FIG. 1, a conventional power monitoring apparatus 1 receives an input voltage 91 from exterior as the power source of a fan 10. Firstly, the input voltage 91 is detected by an analog control chip 11. A starting unit 12 of the power monitoring apparatus 1 switches on the fan 10 when the input voltage 91 is normal. On the other hand, the analog control chip 11 switches off the starting unit 12 and stops the operation of the fan 10 when the input voltage 91 is lower than the minimum starting voltage or is higher than the maximum acceptable voltage. It only prevents the internal elements of the fan from being damaged to achieve a voltage protection, but the fan 10 can still be operated when the input voltage 91 is not lower than the minimum starting voltage or is not higher than the maximum acceptable voltage. The abnormal input voltage 91 of the fan 10 is not highlighted, which is possible to lead to an unexpected operation and affects the reliability of the fan 10.
Therefore, it is imperative to provide a power monitoring apparatus to solve the above-mentioned problems.